The invention relates to the field of fingerprint processing, and, more particularly, to the field of creating a database of fingerprint data and matching a new fingerprint to the database.
Fingerprint matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof, converting it into electrical signals, and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample or new fingerprint may be compared to information for reference fingerprints already in storage to determine or verify a person""s identity.
Unfortunately, comparing a sample fingerprint to a large number of reference fingerprints may be prohibitively expensive and/or simply take too long. Accordingly, fingerprints are typically classified into a plurality of discrete sets and/or subsets in the form of a hierarchical tree to thereby expedite searching. For example, a common top level classification for fingerprints usually differentiates the prints into the classes of: plain whorl, plain loop, tented arch, etc. based upon broad ridge pattern types. These classes may be yet further divided into subclasses. Accordingly, a fingerprint sample to be searched, once itself classified, can be more efficiently compared to only those prints in the respective classes and subclasses of the search tree. For example, U.S. Pat. No. 5,465,303 to Levison et al. describes both the widely used Henry classification system and the Vucetich classification system.
When the quality of the original copy of a fingerprint is bad, the print may contain many local distortions of the ridge pattern which may result in incorrect orientation of the fingerprint. U.S. Pat. No. 5,140,642 to Hsu et al. is directed to a method for determining the actual position of a core point of a fingerprint based upon finding ridge flows and assigning a direction code, correcting the ridge flows, and allocating the core point based upon the corrected direction codes. Along these lines, U.S. Pat. No. 5,040,224 to Hara discloses an approach to preprocessing fingerprints to correctly determine a position of the core of each fingerprint image for later matching by minutiae patterns.
Fingerprint minutiae, the branches or bifurcations and end points of the fingerprint ridges, are often used to determine a match between a sample print and a reference print database. For example, U.S. Pat. Nos. 3,859,633 and 3,893,080 both to Ho et al. are directed to fingerprint identification based upon fingerprint minutiae matching.
U.S. Pat. No. 4,151,512 to Riganati et al. describes a fingerprint classification method using extracted ridge contour data. The ridge flow in the fingerprint pattern and minutiae data are identified and extracted from a fingerprint pattern. Topological data, identifying singularity points such as tri-radii and cores, as well as ridge flow line tracings related to those points are extracted from the ridge contour data. The extracted information is used to automatically perform classification of the fingerprint patterns and/or matching of the fingerprint pattern with patterns stored in a mass file.
U.S. Pat. No. 5,845,005 to Setlak et al., and assigned to the assignee of the present invention, discloses a significant advance in the area of fingerprint indexing and searching of a database of reference fingerprints to determine a match. In particular, index values are calculated which are generally evenly distributed and continuous over a relatively large population of individuals. The index values may be determined based upon ridge flow curvature of the fingerprints. A particularly advantageous index, called a curliness index, is disclosed and this index is based upon an aggregate of a magnitude of a rate of change of ridge flow direction vectors.
Other important advances have also been made in the area of integrated circuit fingerprint sensors, as disclosed, for example, in U.S. Pat. Nos. 5,828,773 and 5,862,248, both assigned to the assignee of the present invention. The disclosed sensors are based upon generating an electric field which can sense the ridges of a fingerprint despite contamination, skin surface damage, and other factors. The sensor is relatively compact and rugged.
Despite improvements in sensor technology and in fingerprint enrollment and matching approaches, processing is still computationally intensive thus limits widespread use of fingerprint sensing. A large computational burden may slow matching operations and/or add significantly to the cost of a fingerprint sensor.
In view of the foregoing background, it is therefore an object of the present invention to provide a method and related fingerprint apparatus that has a reduced computational processing burden, such as for matching a new fingerprint to an enrolled fingerprint.
This and other objects, features and advantages in accordance with the present invention are provided in one embodiment by a method for enrolling at least one fingerprint and determining a match of a new fingerprint thereto using data related to fingerprint ridge flow, and wherein, for matching, a desired area segment of the new fingerprint is compared to a corresponding area segment stored in a database. Accordingly, the computations are greatly simplified. In particular, the method preferably comprises: generating and storing enrollment data based upon fingerprint ridge flow over a plurality of predetermined area segments for the at least one fingerprint, sensing a new fingerprint, and generating sensed data based upon fingerprint ridge flow of the new fingerprint over at least one desired area segment of the plurality of predetermined area segments. The method also preferably includes comparing the enrollment data and sensed data to determine whether the new fingerprint matches an enrolled fingerprint.
The step of generating sensed data preferably comprises identifying and generating sensed data for only a single desired area segment in one embodiment. In another embodiment, a plurality of area segments are identified and processed to achieve a desired performance. For example, the desired performance may comprise at least one of a desired false acceptance rate and a desired false reject rate. The data generated for the desired segment areas based upon ridge flow are advantageously statistically independent to thereby provide better matching accuracy.
The steps of generating enrollment data and sensed data may each comprise generating ridge flow direction vectors. More particularly, the steps of generating enrollment data and sensed data may each comprise generating aggregates of rates of change of fingerprint ridge flow direction vectors.
The step of sensing the new fingerprint may comprise sensing the new fingerprint over an entire fingerprint sensing area. Accordingly, the step of generating sensed data preferably comprises identifying and generating sensed data over only a portion of the entire fingerprint sensing area corresponding to the at least one desired area segment. In addition, the step of sensing the new fingerprint preferably comprises sensing the fingerprint using a fingerprint sensing integrated circuit, which is relatively compact and rugged.
Another aspect of the invention relates to a fingerprint sensing apparatus performing the method steps recited above. More particularly, the apparatus in one embodiment preferably comprises a fingerprint sensing area, and an enrollment circuit connected to the fingerprint sensing area for enrolling a fingerprint of a user by generating and storing enrollment data based upon fingerprint ridge flow over a plurality of predetermined area segments for the at least one fingerprint.
The fingerprint sensing apparatus may also preferably further include a match determining circuit. The match determining circuit determines a match of a new fingerprint to an enrolled fingerprint by sensing a new fingerprint using the fingerprint sensing area, and generating sensed data based upon fingerprint ridge flow of the new fingerprint over at least one desired area segment of the plurality of predetermined area segments. The match determining circuit preferably includes a comparor for comparing the enrollment data and sensed data to determine whether the new fingerprint matches an enrolled fingerprint.
In one embodiment, the match determining circuit preferably identifies and generates sensed data for only a single desired area segment. In another embodiment, the match determining circuit of the apparatus identifies and generates sensed data for a plurality of desired area segments to achieve a desired performance.